<html>

</html>
<body>
    <div>
        <button class="btn">显示</button>
        <div class="test" style="border: 1px solid red;height: 20px;">
            <div class="myclass" style="display: none;">测试1</div>
        </div>
    </div>
</body>
<style>
.test:hover{
    background-color: green;
}
</style>